Device Having a Molded Seal

ABSTRACT

The invention relates to a device having at least one first component ( 2 ) and having a second component ( 1 ) which is arranged so as to be movable relative to the first component ( 2 ), characterized in that a molded seal ( 16 ) is arranged in a groove ( 20 ) of the first component ( 2 ), which molded seal is in contact with the second component ( 1 ), wherein a first chamber( 3 ) formed on one side of the molded seal ( 16 ) between the first and the second component can be charged with a first pressure and a second chamber ( 33 ) formed on the opposite side of the molded seal ( 16 ) between the first and the second component can be charged with a second pressure, and the molded seal ( 16 ) together with the first component ( 2 ) forms at least one overflow valve.

The present invention generally relates to a device having at least one first component and one second component which is arranged so as to be movable relative to the first component, as per the preamble of claim 1.

Such devices are known for example as compressed-air control cylinders, for example for the actuation of a vehicle clutch in a heavy goods vehicle or omnibus. Such a compressed-air control cylinder is known for example from EP 1 344 949 B1. It is proposed in that document that a check valve be arranged in the end wall of the housing of the control cylinder. In this way, the control cylinder is improved such that small leakages in the aeration valve do not lead to an undesired pressure build-up and therefore to a deployment of the control cylinder piston rod.

It is an object of the present invention to improve over a device of the type specified in the preamble of claim 1 such that the problem specified in EP 1 344 949 B1, that of compensating small leakages, is solved in a more cost-effective manner.

This object is achievable by means of the inventive embodiment specified in claim 1. The subclaims specify advantageous further embodiments of the invention.

According to an embodiment of the present invention, the problem of compensating an undesired pressure arising as a result of a small leakage is solved in a simple manner, without the use of additional components. A molded seal, which is required in the device in any case for providing sealing between two pressure chambers, can be used together with a part of the device to form an overflow valve. This has the advantage that no additional components are required, and therefore the invention can be realized in a very cost-effective manner. This advantageously includes the molded seal, which is to be understood to mean a seal with a certain, generally asymmetrical cross-sectional profile. As a result of the profiling, the molded seal has a defined position within the device—in contrast to an O-ring, for example.

An overflow valve is a valve which closes above a certain pressure value or above a difference of pressures and opens below said pressure or said pressure difference. In one embodiment of the invention, the overflow valve is designed so as to compensate leakages of up to 1.5 bar, that is to say the overflow valve separates the first chamber from the second chamber only when a pressure value of 1.5 bar is exceeded.

In one embodiment of the invention, a restoring element is provided, by means of which the overflow valve can be acted on in the opening direction. Through corresponding dimensioning of the restoring element, it is possible to set a desired closing pressure of the overflow valve. The restoring element may for example be in the form of a compression spring or tension spring.

In one embodiment of the invention, the molded seal has at least one closable passage duct via which the first chamber can be connected to the second chamber. This permits a simple realization of the overflow valve in existing designs of molded seals. The passage duct may be realized for example in the form of a bore.

In one embodiment of the invention, the passage duct can be closed off by a wall of the groove.

In one embodiment of the invention, the groove width is greater than the width of the molded seal. Here, the molded seal can be displaced within the groove, that is to say over the extent of the groove width, as a result of a pressure difference between the first and the second pressure. The desired valve function of the overflow valve can be realized by means of the displaceability of the molded seal. In combination with the refinement that the passage duct can be closed off by a wall of the groove, the overflow valve can be realized in a simple manner.

In one embodiment of the invention, at least one restoring element is arranged between the groove wall and that side of the passage duct of the molded seal which can be sealed off by means of the groove wall. A restoring element of this type generates a certain force by means of which the overflow valve can be acted on in the opening direction. The restoring element may be realized for example in the form of a spring.

In one embodiment of the invention, the molded seal has, on that side of the passage duct which can be sealed off by means of the groove wall, at least one restoring element which projects from the surface of the molded seal. In this way, the restoring element may advantageously be formed so as to be integrated into the molded seal. This has advantages during the assembly of the device according to the invention because the restoring element need not be installed as a separate component, but rather is installed simultaneously with the insertion of the molded seal. The restoring element may advantageously also be produced from the material of the molded seal. If an elastic material is used, the restoring element generates a resilient force, the magnitude of which can be selected through corresponding shaping of the restoring element and the material elasticity.

In one embodiment of the invention, the overflow valve has, on the outflow side, an air guide by means of which outflowing air is directed at an angle towards the surface of the first and/or second component. As a result, the outflowing air flows not parallel or perpendicular to the surface but rather impinges on the surface at an angle, that is to say at an angle not equal to the value 0 degrees or 90 degrees. Such an air guide has the advantage that the air flow can blow undesired dust away from the surface of the first and/or second component, and a dust-free or at least low-dust environment can thus be maintained in said region. This has advantages in particular if the device according to the invention is used for the actuation of a vehicle clutch, because in such installation situations, increasing amounts of dust are generated as a result of clutch abrasion. The air guide may be integrated into the molded seal, the first component or into the molded seal and the first component.

In one embodiment of the invention, the molded seal is in the form of a molded sealing ring, in particular in the form of a lip sealing ring. This permits the use of common, commercially available components. In one advantageous embodiment of the invention, a multiplicity of restoring elements is arranged distributed over the circumference of the molded sealing ring.

In one embodiment of the invention, the device has the following further features:

-   -   a) the first component is a compressed-air-actuable piston,     -   b) the second component is a cylinder,     -   c) the piston is arranged in the cylinder,     -   d) the first chamber is a compressed-air actuation chamber for         compressed-air actuation of the piston,     -   e) the compressed-air actuation chamber is formed between the         piston and the cylinder and is sealed off by the molded seal.

This permits a cost-effective realization of a compressed-air-actuable control cylinder with integrated overflow valve.

In one embodiment of the invention, the device has the following further features:

-   -   a) the piston is in the form of an annular piston,     -   b) the cylinder is in the form of an annular cylinder,     -   c) the annular piston is arranged concentrically in the annular         cylinder.

This permits the more cost-effective realization of a compressed-air-actuable control cylinder in the form of a concentric control cylinder. It is possible in this way in particular to realize a device having an annular cylinder and having an annular piston arranged concentrically on the annular cylinder, wherein a substantially annular pressure medium chamber is formed between the annular cylinder and the annular piston, and wherein the annular piston is movable relative to the annular cylinder when the pressure medium chamber is charged with pressure.

In one embodiment of the invention, the device is in the form of a clutch actuation control cylinder for the actuation of a vehicle clutch.

The invention will be explained in more detail below on the basis of exemplary embodiments and with reference to the accompanying drawings, in which:

FIG. 1 shows a device according to the invention in a sectional illustration, and

FIG. 2 shows, in an enlarged sectional illustration, the overflow valve realized in the device as per FIG. 1, and

FIGS. 3 and 4 show embodiments of a molded seal in plain view.

In the figures, the same reference numerals are used for corresponding elements.

FIG. 1 shows the device according to the invention in a sectional illustration, wherein only one half of the device is illustrated because the device is symmetrical, and the other half which is not illustrated is of identical construction.

It is possible to see an annular cylinder 1 having a substantially cylindrical opening 28 which is continuous in the centre in the direction of a longitudinal axis L of the annular cylinder 1. When the annular cylinder is used as an actuating device for a vehicle clutch, the transmission shaft can be guided through the opening 28. The annular cylinder 1 has a first diameter in the region of the opening 28. In a transition region 26, the diameter of the annular cylinder increases to a second, larger diameter to a wall 29. The annular wall 29 may serve for example as a receptacle for a centring flange of a transmission. In this way, the device illustrated in FIG. 1 can be quickly mounted in a centred fashion on a transmission. The annular cylinder 1 extends onward beyond a rear wall 24. In an outer flange region of the rear wall 24 there is provided a fastening opening 25 by means of which the annular cylinder can be screwed to a holding plate of a transmission. The annular cylinder 1 furthermore extends away from the rear wall 24 again in a region 31 formed as an outer wall. In this way, the annular cylinder forms an annular cavity between the wall 32, which delimits the opening 28, and the outer wall 31.

It can also be seen that lamellar reinforcement ribs 27 are provided in the region of the transition from the first to the second inner diameter of the annular cylinder 1, which reinforcement ribs extend along the longitudinal axis L and furthermore outward in the radial direction from the wall 32 which delimits the opening 28. The reinforcement ribs 27 are of relatively narrow construction, wherein the spacing between two reinforcement ribs may be for example approximately three times as large as the width of a reinforcement rib. As can likewise be seen in FIG. 1, the reinforcement ribs 27 have a form such that a transmission of force from the annular cylinder region with the smaller diameter into the region with the larger diameter is distributed uniformly in the material.

An annular piston 2 is arranged on the annular cylinder 1. The annular piston 2 forms, with the side walls 31, 32 of the annular cylinder 1 and the rear wall 24, a pressure medium chamber 3 which can be acted on with pressure medium, for example compressed air, via a pressure medium supply opening 4. On the annular cylinder 2 there is arranged an actuation plate 9 by means of which a clutch release element 10 is acted on with force upon pressurization of the pressure medium chamber 3. The actuation plate 9 is connected to the annular cylinder 2 via a ball bearing 8 and a ball receiving ring 7. Here, the ball receiving ring 7 is fixedly connected to the annular cylinder 2, for example by being pressed or screwed in.

Within the pressure medium chamber 3 there is arranged a compression spring 30. By means of the compression spring 30, the annular piston 2 is pressed under slight preload against the clutch release element 10 via the actuation plate 9. The annular cylinder 2 is held in a defined position in the pressureless state by the compression spring 30.

The annular cylinder 1 has an inner running surface 5 and an outer running surface 6 for the annular piston 2. All of the sealing and scraper elements 11, 12, 13, 14, 16 which act between the annular piston 2 and the annular cylinder 1 are fastened directly to the annular piston 2, that is to say without additional components such as, for example an intermediate piece or an additional retaining element. On the inner side of the annular piston 2 there are provided annular seals 11, 12, 13, 14 which are in contact with the inner running surface 5. On the outer circumference of the annular piston 2, a lip sealing ring 16 is arranged in an encircling outer groove 20 of the annular piston 2. The lip sealing ring 16 bears with its sealing lip against the outer running surface 6 of the annular cylinder 1. Above the lip sealing ring 16 there is formed an annular chamber 33. The lip sealing ring 16 has a passage duct 17 via which the pressure medium chamber 3 can be connected to the annular chamber 33.

The annular cylinder 1 and the annular piston 2 can be produced from cast aluminium. On the annular cylinder 1, both the inner running surface 5 and also the outer running surface 6 can be anodized.

In the region 31, the annular cylinder 1 has radial reinforcement ribs 21, 22, 23, 47, 48 which encircle the longitudinal axis L of the annular cylinder.

As can be seen, the present invention can be advantageously used not only in the concentric control cylinder described on the basis of the embodiment depicted in FIG. 1, but rather also in any pressurizable devices in which a molded seal is provided between two pressurizable chambers.

FIG. 2 shows a detail of the device as per FIG. 1 in the vicinity of the lip sealing ring 16. It is possible to see the housing part 31 of the annular cylinder 1, the annular piston 2 and the lip sealing ring 16 arranged in the groove 20. As can be seen, the groove 20 is wider than the width of the lip sealing ring 16. As a result, the lip sealing ring 16 is displaceable in the longitudinal direction. As can be seen, the lip sealing ring 16 is with a sealing lip 52 which bears against the inner wall 6 of the housing region 31 and which seals off the pressure medium chamber 3 with respect to the annular chamber 33, which is connected to the atmosphere.

The lip sealing ring 16 has a passage duct 17 via which, in the position of the lip sealing ring 16 illustrated in FIG. 2, the pressure medium chamber 3 is connected to the annular chamber 33. On the side facing towards the annular chamber 33, the lip sealing ring 16 has a restoring element 50 which may be arranged for example substantially annularly around the outflow opening of the passage duct 17. Here, the passage duct 17 and the restoring element 50 interact with a wall 51 of the groove 20 so as to form the overflow valve. The restoring element 50 has a side wall 53 which may run obliquely.

In the event of an increase of the pressure in the pressure medium chamber 3, the lip sealing ring 16 is situated initially in the position illustrated in FIG. 2. Here, air can escape from the pressure medium chamber 3 through the passage duct 17 into the annular chamber 33 and thus into the atmosphere. In the event of an increase of the pressure in the pressure medium chamber 3 above a predefined closing pressure, as a result of the relatively small passage cross section of the passage duct 17, a corresponding dynamic pressure builds up which causes the lip sealing ring 16 to be moved to the left towards the wall 51 of the groove 20. As a result, the passage duct 17 is closed off by the wall 51 and the overflow valve is thereby closed. In said state, no further compressed air can escape from the pressure medium chamber 3.

If the pressure in the pressure medium chamber 3 decreases below an opening pressure, the restoring element 50, which may be formed for example from elastic material of the lip sealing ring 16, causes a restoring movement of the lip sealing ring 16 at least to such an extent that air can again escape from the pressure medium chamber 3 via the passage duct 17 into the annular chamber 33 and thus into the atmosphere. The gap 15 generated here by the restoring element 50 between the lip sealing ring 16 and the wall 51 is illustrated on an exaggeratedly large scale in FIG. 2 for illustrative purposes. In practice, the gap is selected to be relative, but sufficient to allow undesired compressed air to escape from the pressure medium chamber 3.

Here, the air flowing out via the passage duct 17 into the annular chamber 33 is diverted at a certain angle by means of an air guide 55 which may be formed as an oblique shoulder of the lip sealing ring 16, such that the air impinges on the outer running surface 6 of the annular cylinder 1 at an angle. Here, the outflowing air has the additional advantageous effect that dust which has accumulated on the running surface 6 is blown away.

FIG. 3 shows an embodiment of a passage opening 17 and of the restoring element 50 on the lip sealing ring 16 in a plan view of a segment of the lip sealing ring 16. As can be seen, it is also possible for a plurality of passage ducts 17 with corresponding restoring elements 50 to be provided. The annular restoring elements 50 each have outflow openings 56 in the form of a passage duct. Via the outflow openings 56, the air flowing out of the passage opening 17 can escape from the annular chamber formed by the annular restoring element 50.

FIG. 4 shows restoring elements in the form of rectangular elevations 54 on the lip sealing ring 16. In each case one pair of elevations 54 is arranged on opposite sides of a passage duct 17. The elevations 54 are of relatively flat form, such that adequate sealing of the passage ducts 17 can still be attained if a correspondingly high pressure prevails in the pressure medium chamber 3. Here, the pressure in the pressure medium chamber 3 causes a certain deformation in the form of bending of the lip sealing ring 16, as a result of which the outlet openings of the passage ducts 17 are pressed against the wall 51 and thereby closed off. 

1. A device having at least one first component (2) and one second component (1) which is arranged so as to be movable relative to the first component (2), characterized in that a molded seal (16) is arranged in a groove (20) of the first component (2), which molded seal is in contact with the second component (1), wherein a first chamber (3) formed on one side of the molded seal (16) between the first and the second component can be charged with a first pressure and a second chamber (33) formed on the opposite side of the molded seal (16) between the first and the second component can be charged with a second pressure, and the molded seal (16) forms, together with the first component (2), at least one overflow valve.
 2. The device according to claim 1, characterized in that at least one restoring element (50, 53, 54) is provided, by means of which the overflow valve can be acted on in the opening direction.
 3. The device according to one of the preceding claims, characterized in that the molded seal (16) has at least one closable passage duct (17) via which the first chamber (3) can be connected to the second chamber (33).
 4. The device according to claim 3, characterized in that the passage duct (17) can be closed off by a wall (51) of the groove (20).
 5. The device according to one of the preceding claims, characterized in that the groove width is greater than the width of the molded seal (16), wherein the molded seal (16) can be displaced within the groove (20) as a result of a pressure difference between the first and the second pressure.
 6. The device according to one of claims 2 to 5, characterized in that at least one restoring element (50, 53, 54) is arranged between the groove wall (51) and that side of the passage duct (17) of the molded seal (16) which can be sealed off by means of the groove wall (51).
 7. The device according to claim 6, characterized in that the molded seal (16) has, on that side of the passage duct (17) which can be sealed off by means of the groove wall (51), at least one restoring element (50, 53, 54) which projects from the surface of the molded seal.
 8. The device according to one of the preceding claims, characterized in that the overflow valve has, on the outflow side, an air guide (55) by means of which outflowing air is directed at an angle towards the surface (6) of the first and/or second component (1, 2).
 9. The device according to one of the preceding claims, characterized by the following features: a) the first component is a compressed-air-actuable piston (2), b) the second component is a cylinder (1), c) the piston (2) is arranged in the cylinder (1), d) the first chamber is a compressed-air actuation chamber (3) for compressed-air actuation of the piston (2), e) the compressed-air actuation chamber (3) is formed between the piston (2) and the cylinder (1) and is sealed off by the molded seal (16).
 10. The device according to claim 9, characterized by the following features: a) the piston is in the form of an annular piston (2), b) the cylinder is in the form of an annular cylinder (1), c) the annular piston (2) is arranged concentrically in the annular cylinder (1).
 11. The device according to one of the preceding claims, characterized in that the device is in the form of a clutch actuation control cylinder for the actuation of a vehicle clutch. 